This invention relates to an arrangement for providing a non-vibrating structure for an outboard motor and more particularly to an improved and simplified arrangement for damping vibrations and preventing their emanation from the drive shaft housing of an outboard drive.
In both the outboard drive portion of an inboard/outboard drive and in the drive shaft housing of an outboard motor, the drive shaft housing is normally formed from a unitary, generally hollow casing. The opposite side walls of this casing can act as resonant devices which will amplify the sounds and vibrations generated by the other components of the outboard drive unit. Normally, the drive shaft housing is provided with a hollow interior that forms an expansion chamber that is utilized in conjunction with the silencing of the exhaust gases of the associated powering internal combustion engine. The exhaust gases are delivered to this expansion chamber through an exhaust pipe that extends into the drive shaft housing for expansion and discharge to the atmosphere through an under water exhaust gas outlet. The pulsations of the exhaust gases are one of the sources of sound which will cause the side walls of the drive shaft housing to vibrate and amplify the generated noises. In addition, the exhaust pipe itself is normally not supported, except at its upper end, and it itself can vibrate and transmit noises back through its supporting plate to the atmosphere.
Various arrangements have been employed for attempting to silence these noises, however, they are generally quite complicated and add significantly to the cost and weight of the unit.
It is, therefore, a principal object of this invention to provide an improved, simplified and low cost arrangement for reducing the amount of noise generated by the drive shaft housing of an outboard drive.
It is a further object of this invention to provide an improved arrangement for reducing sound transmission from a drive shaft housing.
It is a yet further object of this invention to provide an improved arrangement for preventing vibrations of the walls of the drive shaft housing and for damping vibrations of an exhaust pipe that extends into the drive shaft housing.